Updated measurements of [O III] 88 $\hat{I}¼$m, [C II] 158 $\hat{I}¼$m, and Dust Continuum Emission from a z=7.2 Galaxy

Abstract

We present updated measurements of the [O III] 88 $\hat{I}¼$m, [C II] 158 $\hat{I}¼$m, and dust continuum emission from a star-forming galaxy at $z=7.212$, SXDF-NB1006-2, by utilizing Atacama Large Millimeter/submillimeter Array (ALMA) archival data sets analysed in previous studies and data sets that have not been analysed before. The follow-up ALMA observations with higher angular resolution and sensitivity reveal a clumpy structure of the [O III] emission on a scale of $0.32-0.85\mathrm{kpc}$. We also combined all the ALMA [O III] ([C II]) data sets and updated the [O III] ([C II]) detection to $5.9\ddot{I}ƒ$ ($3.6\ddot{I}ƒ-4.5\ddot{I}ƒ$). The non-detection of [C II] with data from the REBELS large program implies the incompleteness of spectral-scan surveys using [C II] to detect galaxies with high star formation rates (SFRs) but marginal [C II] emission at high-$z$. The dust continuum at 90 $\hat{I}¼$m and 160 $\hat{I}¼$m remains undetected, indicating little dust content of $<3.9\times 10^6{M}_{\odot }(3\ddot{I}ƒ)$, and we obtained a more stringent constraint on the total infrared luminosity. We updated the [O III]/[C II] luminosity ratios to $10.2\pm 4.7(6.1\pm 3.5$) and $20\pm 12(9.6\pm 6.1$) for $4.5\ddot{I}ƒ$ and $3.6\ddot{I}ƒ$ [C II] detections, respectively, where the ratios in the parentheses are corrected for the surface brightness dimming effect on the extended [C II] emission. We also found a strong [C II] deficit ($0.6-1.3$ dex) between SXDF-NB1006-2 and the mean $L_{[\mathrm{CII}]}-\mathrm{SFR}$ relation of galaxies at $0<z<9$.

13 pages, 10 figures, 8 tables, published in ApJ